1. Field of the Invention
This invention relates to a syncrude composition having improved pour point characteristics and to a method for reducing the pour point of syncrudes, such as those from oil shale, tar sands, oil-impregnated diatomite ore, or coal. More particularly, the invention relates to such a composition and method wherein the transportability of the syncrude composition, as through a pipeline or in a carrier vessel is improved.
2. DESCRIPTION OF THE PRIOR ART
There are many sources of syncrudes from which a wide variety of hydrocarbon products can be made. Among these are such syncrudes derived from oil shale, tar sands, oil impregnated diatomite ore, and coal. Broadly, these syncrudes are produced and/or recovered by well known procedures. The syncrude is then further processed, i.e., refined, to yield various hydrocarbon products or mixtures. To carry out this further processing, it is oftentimes necessary first to transport the syncrude a considerable distance from its point of origin to the location where the futher processing is carried out. Oftentimes the syncrude is produced in the form of a viscous liquid having a high pour point which liquid can be transported and handled, if at all, only with great difficulty and use of large quantities of energy.
Tar sands or bituminous sands are sand deposits impregnated with dense, viscous petroleum and also contain a small amount of water. The bitumen can be separated from the sand by a wide variety of methods, for example, anhydrous solvent extraction, cold water separation and hot water separation of mined tar sands as well as fire flood, emulsion-steam drive using a hydrocarbon diluent or detonation of a nuclear device in situ. Similar techniques can be used to recover oil from diatomite ore. Syncrudes can be prepared from coal by solvent extraction, thermal decomposition including pyrolysis or carbonization, or hydrogenation in the presence of a catalyst.
While syncrudes are largely composed of hydrocarbon molecules of various types, they usually also contain heterogeneous compounds of carbon and hydrogen combined with sulfur, oxygen, nitrogen and/or other atoms.
For simplicity, further discussion of the method will be centered on the handling of syncrude produced from oil shale, even though the same or similar techniques can also be applied to syncrude derived from tar sand, oil-impregnated diatomite ore, or coal. Oil shales contain an organic portion which is a mixture of complex chemical compounds referred to as "kerogen" and mineral matter. Destructive pyrolysis, or retorting of crushed shale, carried out either above ground or in situ, yields shale oil. Retorting involves the crushing and heating of large quantities of raw shale and the cooling and discharging of almost equally large quantities of spent shale. Ideally a large percentage of the organic portion converts to a liquid, some converts to light gases and the remainder stays as a carbon-rich residue on the mineral matrix. Shale oils produced by conventional retorting processes generally have pour points in the range of 65.degree. to 85.degree. F. Shale oil retorts, for economic reasons, are usually located near the source of the shale, i.e., often in remote areas, such as Colorado. Since the temperature in these areas is frequently below freezing, high pour point shale oil cannot be handled at these low temperatures unless measures are taken to prevent the oil from being cooled below its pour point and setting up. Since it may be desirable to transport the syncrude, i.e., shale oil by pipeline or tank car from the retorting site to a location where it may be more conveniently further processed, it is especially important to be able to keep the shale oil from solidifying while it is being transported.
A wide variety of compositions and methods employing a number of different treating agents are known for reducing the pour point of shale oil, for example, U.S. Pat. Nos. 3,523,071 to Knapp et al., 3,532,618 to Wunderlich et al., 3,617,469 to Schilinger et al., 4,240,916 to Rossi, 4,166,023 to Seitzer, 4,172,026 to Jensen and 4,181,177 to Compton.
Likewise, it is known to employ ammonia or ammonium hydroxide to prepare additives to be used in treating hydrocarbons such as shale oil, coal tar oil and the like to remove therefrom nitrogen and other materials. In these processes the hydrocarbons are not directly contacted by either ammonia or ammonium hydroxide.
U.S. Pat. No. 2,943,049 to Nahin et al. describes a method for removing nitrogen bases from hydrocarbons such as crude oil, coal tar oil or shale oil wherein the hydrocarbons are contacted with a synthetic cation exchange resin, such as hydrogen bentonite to form a stable nitrogen-containing solid product which can be physically separated from the hydrocarbons. In preparing the hydrogen bentonite, naturally occurring bentonite is contacted first with a synthetic cationic exchange resin previously treated with ammonium chloride, next with a synthetic anionic exchange resin previously treated with a strong hydroxide, such as sodium hydroxide, and finally with a synthetic cationic exchange resin previously treated with a strong acid. In the treatment with the anionic exchange resin, a dilute solution of ammonium hydroxide forms which is subsequently converted to water by contact with the acid-treated cationic exchange resin.
U.S. Pat. No. 3,778,365 to Hamner et al. discloses a process of subjecting heavy hydrocarbon oils containing appreciable quantities of nitrogen, such as crude oil and shale oil, to catalytic hydrocracking and hydrodenitrogenation in the presence of hydrogen and a catalyst prepared by a method involving ammonia activation of a catalyst composite, such as a mixture of non-noble metals deposited on a suitable cracking base, for example, a zeolite. The ammonia activation can be carried out with gaseous ammonia or an ammonia precursor, such as an aliphatic or aromatic amine or a nitrile.
U.S. Pat. No. 3,025,231 to Friedman et al. shows a method for removing organic matter, sulfur and metals from crude shale oil by hydrogenation in the presence of an activated carbon catalyst. As part of the preparation of the catalyst, it is treated with an aqueous solution of concentrated ammonium hydroxide.
While each of the aforementioned compositions and methods has met with some success in particular applications, the need exists for a further improved composition and method for lowering the pour point of syncrudes.
Accordingly, a principal object of this invention is to provide a composition and method for treating syncrudes such as those derived from oil shale, tar sands, oil-impregnated diatomite ore, coal and the like, to reduce the pour point of such syncrudes.
A further object of this invention is to provide such a composition and method wherein the pour point is lowered sufficiently so that the syncrude is in the liquid form at ambient temperature.
A still further object of this invention is to provide such a composition and method wherein the transportability of the syncrude through a pipeline or other conduit is improved.
Yet another object of this invention is to provide such a composition and method wherein the initial wax crystallization temperature of the syncrude is lowered.
Other objects, advantages and features of this invention will become apparent to those skilled in the art from the following description and appended claims.